Integrated testis transcriptome and whole genome analysis of sexual maturity in Large White and Tongcheng pigs

Testicular development and spermatogenesis play critical roles in male fertility and sexual maturation. To explore the genetic basis and key genes related to sexual maturity, we measured serum testosterone content and analysed testis tissue sections of Large White (LW) and Tongcheng (TC) boars at an immature age. We then screened differentially expressed genes (DEGs) in testis development in both breeds using RNA-seq. Finally, we analysed the selection signatures of both breeds to investigate which DEGs were subjected to positive selection. Our findings showed that serum testosterone contents in TC pigs (similar to 4 ng/mL) were much higher than those in LW pigs (<0.95 ng/mL). Haematoxylin and eosin staining of testicular sections showed that the cross-sectional areas and perimeters of the seminiferous tubules in TC testes were larger and longer than those in LW pigs. A total of 5068 DEGs were selected by filtering criteria of q value <0.05 and |log(2)(fold change)| >= 1. Gene Ontology analysis revealed that 250 genes were enriched in 11 biological process categories involved in sexual maturity. Most candidate genes, including TRIP13, NR6A1, STRA8, PCSK4, ACRBP, TSSK1B and TSSK6, were under positive selection. These results provide a better understanding of the genetic basis for testicular maturation and are useful for enhancing boar reproductive traits through molecular breeding.